JPH05336125A - Communication system - Google Patents

Abstract

PURPOSE:To set a component and to revise it almost without decreasing an effective communication speed by forming the system with a master node controlling the polling/selecting system and slave nodes whose maximum connection number is N connecting to the master node. CONSTITUTION:The communication system is built up by slave nodes 1-4 making transmission to a master node 10 with a 1st specific message at the starting of the system and sending a response message upon the receipt of a 2nd specific message from the master node 10 and by the master node 10 sending the 2nd specific message to the slave nodes 1-4 upon the receipt of the 1st specific message or a broken message and discriminating the connection/nonconnection of the slave nodes 1-3 based on the transmission reception state of the 1st specific message, the 2nd specific message and the response message. Thus, the system components are set automatically almost without decreasing an effective communication speed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication system for controlling communication by a polling / selecting method.

[0002]

2. Description of the Related Art Conventionally, contention methods and polling / selecting methods are known as data communication methods for information devices.

Of these, the contention method is highly expandable in the system, but it requires acquisition of a transmission right and recovery processing in the event of a communication collision, and thus hardware and protocols are complicated. Required. Moreover, since communication data is lost in the event of a collision, there is a drawback that transmission efficiency is reduced.

On the other hand, in the polling / selecting method, since the communication flow is centrally managed by the control node (parent node), no complicated processing such as transmission right and recovery in the case of collision is required, so that a relatively simple hardware is used. It can be realized by software and protocol.

In the polling / selecting method, the parent node needs to know the components of the communication system (the number of child nodes, the address of each node, etc.). , A method entered by the user (hereinafter referred to as the first method), or a method of automatically sending and receiving a specific message to automatically judge (hereinafter referred to as the second method)
Method) is adopted.

[0006]

However, in the above-mentioned prior art, when the constituent elements of the communication system are changed,
In particular, the following drawbacks are associated with the addition.

First, in the first method, the user has to re-enter the settings each time a change is made.

In the second method, although the setting is automatically performed by sending and receiving the specific message at regular intervals, the communication traffic increases accordingly.
Accompanied by a decrease in effective transmission efficiency. In particular, if it is attempted to immediately respond to a change in the configuration, the regular interval must be shortened, but the transmission efficiency will be reduced accordingly, so that the transmission band cannot be effectively used.

Further, as a modification of the second method, a method of transmitting / receiving a specific message only when the system is started up can be considered. This method does not reduce the effective transmission efficiency, but has the drawback that the system must be restarted every time a change is made.

It is an object of the present invention to provide a communication system capable of setting and changing the constituent elements in the polling / selecting system with almost no reduction in the effective communication speed.

[0011]

According to the present invention, a first specific message is transmitted to a parent node when a system is started up, and a response message to the second specific message is received when a second specific message is received from the parent node. And a second specific message when the first specific message and the broken message are received, the second specific message is transmitted to the child node, and the first specific message, the second specific message, and the response message. It establishes a communication system with a parent node that determines connection / disconnection of each child node based on the transmission / reception status of each node, and can automatically set the components without substantially reducing the effective communication speed. is there.

[0012]

1 is a block diagram showing a connection form of a communication system according to a first embodiment of the present invention.

This communication system is composed of a parent node 10 which controls the polling / selecting system, and child nodes 1 to 4 which can be connected to the parent node 10 up to N in number. The numbers of the child nodes 1 to 4 directly correspond to the addresses of the child nodes. Also,
The address of the parent node 10 may be an appropriate number other than 1 to N.

A bus-like wiring is provided between each node with a pair of cables. More specifically, the outputs of the parent node are connected to the inputs of all the child nodes, and the outputs of all the child nodes are connected to the inputs of the parent node.

Then, full-duplex communication is possible between the parent node 10 and any child node. This communication is
This is done on a message-by-message basis.
In addition to the data, information on the address of the other party, the address of the sender, and a check sequence (for example, CRC code) for checking the success or failure of the transmission is added.

Such message communication can be realized by a known communication method using a packet or the like.

FIG. 2 is a schematic diagram showing the communication operation in this embodiment. In order to clearly explain the gist of the present invention, the communication system has already been started up by the parent node 10 and the child nodes 1 and 2, and the child node 3 is set therein.
Described below is the case of newly connecting.

First, the parent node 10 and the child node 2 are in communication with each other, and the response message 21 is returned to the command message 20. Since the transmission of data was not completed by sending and receiving the message once, the command message 23 is continuously issued, and the response message 24 is returned in response thereto. At this time, the child node 3 is connected and started up almost at the same time, and the parent node 10 is issued a first specific message 25 notifying that the child node 3 is newly connected.

In the parent node 10, the response message 24 and the first specific message 25 appear to overlap each other, and as a result, the broken message is received. It should be noted that whether or not it is broken can be determined by the error in the check sequence in the message.

When the parent node 10 receives the broken message as described above, the parent node 10 determines that the new child node has issued the first specific message, and the third node
Is issued to notify that the first specific message 25 has been received. At this time, the parent node 10
Since it is unknown which number of the child node is newly connected, the third specific message 26 is broadcast in the form of a broadcast message (that is, a multicast address) to all the child nodes.

Next, the parent node 10 uses the individual message with the destination address of 1 to N as the second identification for the child nodes of 1 to N in order to determine the changed component of the communication system. Messages 27, 29 and 31 are issued in sequence. When each child node receives the message,
Response messages 28, 30, and 32 corresponding thereto are issued.

Here, the parent node 10 also issues the second specific message to child nodes 4 to N (not shown in FIG. 1). Then, since the response message to it is not returned even after a certain period of time, it is possible to know that these child nodes are not actually connected or not operating.

The purpose of transmitting and receiving the second specific message and the response message to the second specific message is to know whether or not the child node of a certain number is connected. By adding unique attribute information to the node, the parent node 10 can also grasp the information.

Through the series of operations described above, the parent node 10 learns the changed components of the system and makes new settings. After this, the parent node 10 restarts the interrupted processing, but the response message 2
Since No. 4 has been lost due to the superposition with the specific message 25, specifically, the process from the command message 23 is restarted as shown in FIG.

By the way, the parent node 10 is the child node 1,
It is not necessary to issue the second specific message to the child nodes 1, 2 since it knows that 2 is already connected. However, it is conceivable that the child node 1 or 2 may be replaced by another device and started up. In this case, a specific message is also issued, so in order to deal with this, the child nodes 1 to N are sequentially operated. It is preferable to issue the second specific message.

The case where the specific message 25 overlaps with another communication has been described above, but the parent node 10
Is not in a communication state and the specific message 25 can be received as it is, simpler processing is sufficient.

FIG. 3 is a schematic diagram showing the communication operation in that case.

When the parent node 10 receives the first specific message 25 from the child node 3, it knows from the information of the source address in the message that it came from the child node 3. Then, in order to notify the child node 3 that the specific message 25 has been received,
The second specific message 33 is issued.

The response message 34 to the second specific message 33 is not always necessary, but if the above-mentioned node attribute information is also grasped, a response is made. Then, after this, the parent node 10 sets up a new communication system including the child node 3.

Next, the operation relating to transmission / reception of the specific message described above will be described with reference to the flowcharts of FIGS.

FIG. 4 shows the operation of the parent node 10. First, in S100, the arrival of a message is awaited. Next, in S101, it is determined whether or not the received message is a broken message, and if it is normal,
It is determined whether the received message is a specific message (S102). Then, if the received message is not a specific message, the message is for normal communication, and therefore, in S120, processing corresponding to each message is performed.

If the received message is a specific message, in S103, the sender address in the received message is used to recognize which number of the child node is newly connected and direct it to the child node. And issue a second specific message. And S104, S
At 105, the response message to the message is waited for a fixed time, at S106, the attribute information of the child node is known from the data in the response message, and at S107, the new communication system including the new node is set.

If the received message is a broken message in S101, the process proceeds to S108, and the third specific message is issued at the broadcast address. Next, the address is set to 1 in S109, a second specific message is issued with the address as the other party in S110, and a response message to the second specific message is waited for a fixed time in S111 and S112.

When the response message is returned within the time, in S113, it is recognized that the child node of the address number is connected, and the attribute information of the node is grasped. On the other hand, when the response message is not returned within the time, it is recognized in S114 that the child node of the address number is not connected.

Next, in S115, the address is incremented by +1.
Only, and if it does not exceed N in S116, the operation from S110 is repeated. That is, S1
The operations from 10 to S115 are repeated N times. After that, in S107, the communication system is set by the recognized new component.

FIG. 5 shows the operation on the child node side.
First, when a child node rises, in S200,
The first specific message is issued to the parent node 10. Then, in S201 and S202, the reception of the second specific message or the third specific message is waited for a fixed time, and if none of the messages arrives within the time, the process returns to S200.

The second message is the one that arrives in time.
In the case of the third specific message, a response message to the message is issued in S203, and the process proceeds to S204.
Go to 4.

Then, in S204, the arrival of a new message is awaited. In S205, if the message is the third specific message, nothing is done in S204.
Return to. In this case, the received third specific message is
It can be ignored because it corresponds to a specific message issued by another node.

If the message received in S204 is the second specific message, in S206,
Issue a response message to this message. Further, when the message received in S204 is another message, this message is for normal communication, so that the process corresponding to each message may be performed in S210. After that, the operations after S204 are repeatedly executed.

As described above, according to this embodiment,
It is possible to automatically configure its components in response to changes in the communication system. Moreover, since the series of operations related to the setting is only executed when the system is changed, there is an effect that the effective communication speed is hardly reduced.

Next, another embodiment of the present invention will be described.

In the above-mentioned first embodiment, the processing in the case where a new node is added was mainly explained, but if the whole communication system is started up by a method similar to this, it is mentioned above every time one child node is started up. The series of operations
It may take some time to reach a stable state. Therefore, when the entire communication system is started up in this way, a series of operations can be suppressed once or twice by starting up the parent node last.

However, as a more effective method, it is considered that the main power supply of the child node can be turned on / off by the message of the parent node.

In this case, even if the OFF message is received,
The child node does not turn off all power, but powers only the circuits related to communication. Then, when the ON message is issued from the parent node next time, the power supply of the other parts is restored and the operating state is returned to the complete operation. At this time, the specific message is not issued at the time of turning on by the on message, unlike the so-called startup (when the power is turned on from a completely power-off state or at the time of hardware reset).

By enabling remote on / off from the parent node in this way, a series of operations are not executed each time the child node is turned on, and a stable state is immediately obtained. .. Moreover, in this case, even if each child node is discretely arranged, it is not necessary to turn on and turn off the power switches of each child node, which is another advantage.

Of course, the same power supply control as when the off message is received may be implemented by the switch on the child node side.

Further, in the above-mentioned first embodiment, the bus-like communication path has been described as an example, but the present invention is not limited to this, and other topologies such as star-like and daisy-chain are possible. The same can be applied to the above communication path.

Further, the present invention can be implemented in a half-duplex communication path instead of a full-duplex communication path. In this case, the specific message does not reach the parent node while the parent node is transmitting, but as shown in the flowchart of FIG. 5, the new node is until the second or third specific message is issued from the parent node. The issuance of the first specific message is repeated. Therefore, it is possible to reliably deliver (at least in the form of a broken) a specific message to the parent node when the parent node next becomes the receiving state.

Upon receiving the specific message or the broken message, the parent node immediately issues the second or third specific message. It is possible that the second or third specific message overlaps with the message issued by the child node that is performing regular communication, but the child node will be in the receiving state after issuing the message. , The parent node re-enters the receiving state after issuing the second or third specific message,
After confirming that the specific message does not arrive again (if it arrives again, repeat the above operation),
If the subsequent operations are performed, the handshake between the parent node and the new node does not go round.

[0050]

As described above, according to the present invention,
When the child node starts up, the first specific message is issued without permission from the parent node, and after this, the second specific message and the response message to it are sent and received between the parent and child. The components of the communication system can be automatically set.

Further, since the series of operations are performed only when the system is changed, the communication traffic in the normal time is not increased at all, and as a result, the effective communication speed is hardly reduced. Moreover, it is possible to set automatically according to the changes.

Furthermore, when changing the system, it is not necessary to change the existing part at all, and a new node can be connected without even considering whether or not communication is actually being performed. A communication system that is easy to handle can be realized.

[Brief description of drawings]

FIG. 1 is a block diagram showing a system configuration according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing message exchange between a parent node and a child node in the above embodiment.

FIG. 3 is a schematic diagram showing message exchange between a parent node and a child node in the above embodiment.

FIG. 4 is a flowchart showing an operation of a parent node in the above embodiment.

FIG. 5 is a flowchart showing an operation of a child node in the above embodiment.

[Explanation of symbols]

 1 to 4 ... Child nodes, 10 ... Parent nodes.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Shinichi Sunagawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Katsuhiko Nagasaki 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Within the corporation

Claims (2)

[Claims] 1. A communication system comprising a parent node and up to N child nodes and performing communication control by a polling / selecting method, wherein the child node sends a first specific message to a parent when the system is started up. A first issuing means for issuing to the node,
And a second issuing means for issuing a response message to the second specific message from the parent node when the second specific message is received from the parent node; the parent node receives the first specific message from the child node. Sometimes, a third issuing means for issuing a second specific message to the child node which is the sender of the message, and a first issuing means for recognizing the connection with the child node when the specific message is issued.
Recognition means, error detection means for detecting an error in the message received from the child node, and issuing the second specific message to the child nodes 1 to N when the error status message is received. 4 issuing means,
The second recognition means for recognizing the connection / non-connection of each child node from the transmission / reception status of the first specific message, the second specific message and the response message, and the recognition results of the first and second recognition means. A system setting means for automatically setting the components of the communication system based on the above; 2. The communication system according to claim 1, wherein the response message includes attribute information unique to each node.